Rotational speed is often used as a parameter for controlling certain functions. Such is particularly true when rotational speed of a vehicular engine and/or vehicular transmission input or output shaft is used to determine gear-shift points of an automatic or semi-automatic transmission.
Automatic and semi-automatic transmissions utilizing microprocessor controllers for processing speed output signals in accordance with predetermined logic rules to issue output command signals to system activators are known in the art of which examples are disclosed in U.S. Pat. Nos. 4,361,060; 4,595,986 and 4,648,290, the disclosures of which are incorporated herein by reference.
Rotational speed of a rotating member however is frequently not constant and may vary with time for a variety of reasons. Such variations in rotational speed (often characterized as "loping" or "oscillations") present a real problem in determining a mean or approximate speed for visual and more particularly for control purposes.
Variations in speed relative time results in the problem of having to determine an approximate or mean rotational speed from a plurality of discrete rotational speed values within a predetermined time period.
Although a simple arithmetic mean solution may be suitable for some purposes, a well known more accurate method for determining a mean or approximate value from an array of scattered data is the "method of least squares" which determines an estimated value of the instant value being examined according to the equation: ##EQU1##
The problem with this method however is that it involves complex calculations that are slow and time consuming.
In many applications, a rapid and accurate approximation of a mean value must be made which is particularly true on providing approximated mean rotational speed values of a rotating shaft for controlling optimum shifting points for vehicular transmission speed change gears.
In contrast to the above, the present invention establishes conditions by which the above equation is reduced to a family relatively simple linear equations for determining approximate rotational speed of a rotating member whose rotational speed may not be uniform and which can be rapidly determined by microprocessors well known to those skilled in the art.